1. Field of the Invention
The present invention relates to improved balloon catheter devices, and methods of making the same.
2. Description of Related Art
Balloon catheter devices are commonly used for a wide variety of medical procedures today, including temporarily occluding blood or other fluid flow, re-shaping of blood vessels or other body conduits, removing plaque or other obstructions from vessels, and/or delivering or positioning devices within vessels, such as intraluminal stent or stent-graft devices. With on-going advances in minimally invasive medical procedures, such balloon devices continue to grow in popularity and in scope of possible uses.
Traditionally, balloon devices have taken one of two general forms—angioplasty balloons and embolectomy balloons. Angioplasty balloons have generally been constructed from relatively stiff material, such as poly(ethylene terephthalate) (PET), which can be safely inflated to relatively high internal pressures (such as on the order of 10 ATM (1.0 MPa) or more). These balloons generally inflate rapidly to a given maximum diameter and will undergo minimal additional enlargement upon introduction of additional pressure (until they burst under extreme pressures). These balloons are typically used where high pressure is desired, such as to fracture and/or compact hard plaque in a blood vessel or to deliver balloon expandable devices, such as stents. One drawback with stiff angioplasty balloons, however, is that upon deflation they tend to become a crinkled, flattened mass that have dimensions significantly larger than their initial introduction diameter—making them more difficult to remove than to initially introduce. Additionally, these flattened devices in many cases cause adverse interactions between themselves and the devices with which they are conjunctly used.
By contrast, embolectomy balloons are normally constructed from a highly elastomeric material, such as latex, which will enlarge steadily in diameter with a steady increase in internal pressure. These balloons typically are governed by the volume of fluid/liquid used to inflate them rather than an operating pressure, have much lower operating pressures (such as, typically on the order of about 2 ATM (203 kPa) or less) and they tend to continue to grow in diameter upon further introduction of pressure until they ultimately burst. These balloons are typically used in embolic procedures where soft material is repositioned in a vessel. Additionally, the balloon can be formed from a tacky material such as latex that can be used to adhere to soft plaque, thrombus or other undesirable material within a vessel and then withdrawn to remove the undesirable material. Although these balloons have low operating pressures, they do tend to deflate to diameters almost identical to their initial introduction diameters—making them very easy to remove.
It has been a long desired goal to develop a balloon that can withstand the very high pressures required for angioplasty but also has the inflation and deflation characteristics of an embolectomy balloon. The combination of these properties was achieved with the invention of the balloon devices described in U.S. Pat. Nos. 5,752,934 and 5,868,704 to Campbell, et al., and U.S. patent application Ser. No. 08/858,309 to Campbell, et al. These patents describe several important advances in balloon catheter constructions, including how to construct high pressure balloons from expanded polytetrafluoroethylene (PTFE) and an elastomer so as to exhibit steady growth with increasing pressure up to a pre-determined maximum diameter and then readily compact to virtually their initial introduction diameters for easy removal.
The Campbell et al. patents teach how to form a tubular sleeve from expanded PTFE tape and then coat the sleeve with an elastomer. The sleeve is then mounted on a catheter shaft in a manner that allows it to contain expansion liquid (either by mounting the sleeve over an expandable bladder (e.g., a latex or PET balloon) or by rendering the sleeve liquid-tight so as to allow it to serve as the bladder itself). The result is a unique balloon that combines high-pressure performance with compaction to near initial introductory diameter following inflation and deflation. Balloons made in accordance with the Campbell et al. patents have excellent performance characteristics and are particularly suitable for delivery and/or deployment of balloon expandable devices, such as intravascular stents.
Despite the excellent performance characteristics of the Campbell et al. balloons, it is believed that further improvements are desirable in the balloons and their mounting techniques to make them easier to mount on catheter shafts. Further, it is believed that further improvements in balloon performance can be achieved by modifying the mounting techniques, such as to provide a controlled failure mechanism.